diff --git a/glm/gtc/quaternion.hpp b/glm/gtc/quaternion.hpp
index 995ec60c..25f741cc 100644
--- a/glm/gtc/quaternion.hpp
+++ b/glm/gtc/quaternion.hpp
@@ -315,7 +315,7 @@ namespace glm
 	template<typename T, qualifier Q>
 	GLM_FUNC_DECL mat<4, 4, T, Q> mat4_cast(tquat<T, Q> const& x);
 
-	/// Converts a 3 * 3 matrix to a quaternion.
+	/// Converts a pure rotation 3 * 3 matrix to a quaternion.
 	///
 	/// @tparam T Floating-point scalar types.
 	///
@@ -323,7 +323,7 @@ namespace glm
 	template<typename T, qualifier Q>
 	GLM_FUNC_DECL tquat<T, Q> quat_cast(mat<3, 3, T, Q> const& x);
 
-	/// Converts a 4 * 4 matrix to a quaternion.
+	/// Converts a pure rotation 4 * 4 matrix to a quaternion.
 	///
 	/// @tparam T Floating-point scalar types.
 	///
diff --git a/readme.md b/readme.md
index e4fa98d5..cb9da7f8 100644
--- a/readme.md
+++ b/readme.md
@@ -90,7 +90,8 @@ glm::mat4 camera(float Translate, glm::vec2 const& Rotate)
 - Added support of -Weverything with Clang #646
 - Improved exponential funtion test coverage
 - Enabled warnings as error with Clang unit tests
-- Canan package is an external repository: https://github.com/bincrafters/conan-glm
+- Conan package is an external repository: https://github.com/bincrafters/conan-glm
+- Clarify quat_cast documentation, applying on pure rotation matrices #759
 
 #### Fixes:
 - Removed doxygen references to GTC_half_float which was removed in 0.9.4